Thanks! I almost got some naval jelly last night but ended up getting CLR since I've got to work on lime deposits in our bathrooms also. If CLR and additional sanding doesn't work, I'll get some naval jelly. Maybe overdoing it for a non-enthusiast, non-collectible bike but it still has some sentimental value.
Naval Jelly is a no-sand solution. It just dives in and eats up FeO. Just need to rinse it properly after. It's really a no-brainer solution. Just RTFM on the label and you'll be good to go.
But I've never worked w/CLR so maybe it's easier? Dunno.